In this program we propose to study the role that the olfactory bulb plays in the development, maturation and survival of the olfactory sensory neurons. We intend also to study the role that the olfactory sensory neurons play in the development of the olfactory bulb target neurons (mitral and tufted cells). In the first part of the study we will test the behavior of the olfactory neurons in adult rats which were partially or totally deprived of the olfactory bulb as neonatals or adults. We will also, by means of transplantation, substitute the olfactory bulb with the presumptive visual cortex (a non olfactory target) from E14 embryos. The changes in the development, maturation and survival that we expect to be expressed by an altered turnover rate, will be assessed by means of quantitative morphology, 3H Thymidine autoradiography and immunohistochemistry for the demonstration of the olfactory marker protein. These data will be compared with the results obtained in normal animals. In the second part of the program (role of the olfactory sensory neurons in the development of their target (the olfactory bulb)), we will transplant the presumptive olfactory bulb area from E14 rat embryos in place of the olfactory bulb of a neonatal rat (P1) after its olfactory bulb has been totally removed. Furthermore, we will also transplant the same presumptive olfactory bulb area into the parietal cortex of neonatal rats and into the anterior chamber of the eye of adult rats to see their development without the influence of the olfactory input. As a control, the development of the normal olfactory bulb will be studied in stage embryos and postnatal rats. Silver methods, TEM and immunohistochemical techniques will be employed to evaluate the development of the large neurons of the olfactory bulb.